This novel mechanism can help describe the poor response to treatment of this T-LBL patient subgroup, also in agreement with previous studies on HTLV-1-induced adult T cell leukemia (ATL) [35,36] in which IL-13 and IL-4 were demonstrated to sustain proliferative and antiapoptotic functions that lead to leukemogenesis, and in patients with severe asthma in which IL-4 pathway activation is associated with an increased glucocorticoid insensitiveness [37]. Here, IL4 is linked to adult T-cell leukemia/lymphoma.